And I'm Audie Cornish. In Iraq the city of Mosul is becoming the de facto power center for the so-called Islamic State. The Sunni extremist group also known as ISIS took over the large Iraqi city last month as it swept through the northwest of the country. For a couple of years, the group had already controlled large portions of neighboring Syria amid that country's civil war. As it solidifies its hold on Mosul its building a track record for how it actually governs. NPR's Leila Fadel joins us now to discuss the. She's near Mosul in the northern Iraqi city of Erbil. And, Leila, to begin describe daily life under the so-called Islamic State.

LEILA FADEL, BYLINE: Well, residents say that women are being forced to wear face and head coverings, men are wearing baggy pants, smoking is banned and people caught breaking the rules are whipped or killed. ISIS, which calls itself the Islamic State, is solidifying its power in the city they've even put a police force with their own cars and the markings of their state. They have uniforms and badges, they have courts and mosques where people go to repent which means they basically disavow the government and they get an official looking document to say they no longer are loyal to the government they're loyal to the Islamic State. But people are also being executed and going missing every day so there is a growing sense of fear there.

CORNISH: Now, we initially heard many reports that the extremists have looted banks and were extorting money from people in Mosul. What you know about that now a month later?

FADEL: Well, the banks - the reports about the banks - the governor, Nujaifi, who fled Mosul tells us he's really not sure that's true. He says the vault in the bank still hasn't been opened so the $430 million they supposedly took they might not have. And Mosul really has long been a financial source for the Islamic state experts say. Its members have taken protection money from shopkeepers, ransoms for kidnappings. The governor says it's now in control of two oilfields near Mosul and are smuggling oil out through Syria, making money that way. And they also run gas stations, for example, so they make a lot of money. And also recently they forced the Christians in the city to flee and they took everything from them. They called it spoils of war. And most Iraqis don't trust banks so their life-savings are in their homes and that's a treasure trove for this extremist group.

CORNISH: And you mentioned the Christians fleeing over the weekend - are there any left in Mosul now?

FADEL: You know, Christians have been in Mosul since the birth of Christianity 2000 years ago and now basically none are left. The Islamic State gave them an ultimatum - convert, pay a poll tax, leave by Saturday or die by the sword. They mark their homes with red paint and the letter N for Nassarah, a reference to word used for Christians in the Koran, the holy book for Muslims. And so many were forced to leave on foot and even though many don't agree with this merciless and brutal interpretation of Islamic law, they're afraid of these gunmen and afraid to say anything. And it's not only Christians other minorities are also being targeted.

CORNISH: Finally, Leila, when ISIS first came to Mosul there were some residents who actually welcomed them, is that still the case?

FADEL: Well, it's really complicated. When speaking to people from Mosul they talk about the Iraqi army as if it were an occupying force - they were raiding homes, torturing prisoners, even when the Iraqi army left these areas and the Islamic state took over they killed Sunni prisoners as they left according to human-rights watch. So when the Islamic state came to Mosul, they took down these concrete blast walls, they opened the roads and people kind of welcomed them as a liberator. But residents say they took about 20 days and they're really seeing the true and ugly face of the force now. So for now, many people still seem to fear the Iraqi government forces more than this group but we're starting to see some signs that their patients might have its limits. We've heard of Sunni families that say that ISIS has kidnapped relatives and are hosting them hostage as a way to intimidate them so nobody resists.